Methods and devices for channel state information transmission

ABSTRACT

Embodiments of the present disclosure relate to methods and devices for channel state information (CSI) transmission. In example embodiments, a method implemented in a terminal device includes performing a channel estimate between the terminal device and a network device across a predetermined frequency range for a set of beams having different spatial directions; determining, based on the channel estimate, first indication information indicating at least one beam selected from the set of beams and second indication information indicating frequency-related information for the at least one selected beam at a plurality of frequency locations in the predetermined frequency range; and transmitting to the network device the first indication information in a first part of a channel state information (CSI) report and the second indication information in a second part of the CSI report.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Continuation of U.S. application Ser. No. 17/254,630, filed onDec. 21, 2020, which is a National Stage of International ApplicationNo. of PCT/CN2018/092511 filed on Jun. 22, 2018, the disclosures of eachof which being incorporated by reference herein in their entireties.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field oftelecommunication, and in particular, to methods and devices for channelstate information (CSI) transmission.

BACKGROUND

Communication technologies have been developed in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is new radio (NR), for example, 5G radioaccess.

NR is a set of enhancements to the LTE mobile standard promulgated byThird Generation Partnership Project (3GPP). It is designed to bettersupport mobile broadband Internet access by improving spectralefficiency, lowering costs, improving services, making use of newspectrum, and better integrating with other open standards using OFDMAwith a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) aswell as support beamforming, multiple-input multiple-output (MIMO)antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in NR technology.These improvements may be applicable to other multi-access technologiesand the telecommunication standards that employ these technologies. Forexample, in the communication systems, generally Channel StateInformation (CSI) of a communication channel between a terminal deviceand a network device is estimated at the receiving terminal device andfed back to the network device to enable the network device to controltransmission based on the current channel conditions indicated by theCSI. According to the NR technology, it has been proposed that channelproperties for both wideband and subband and for different beams (inMIMO systems) are to be reported in the CSI, which results in a largeoverhead for the CSI transmission.

SUMMARY

In general, example embodiments of the present disclosure providemethods and devices for channel state information (CSI) transmission.

In a first aspect, there is provided a method implemented in a terminaldevice. The method comprises performing a channel estimate between theterminal device and a network device across a predetermined frequencyrange for a set of beams having different spatial directions;determining, based on the channel estimate, first indication informationindicating at least one beam selected from the set of beams and secondindication information indicating frequency-related information for theat least one selected beam at a plurality of frequency locations in thepredetermined frequency range; and transmitting to the network devicethe first indication information in a first part of a channel stateinformation (CSI) report and the second indication information in asecond part of the CSI report.

In a second aspect, there is provided a method implemented in a terminaldevice. The method comprises performing a channel estimate between theterminal device and a network device across a predetermined frequencyrange for a set of beams having different spatial directions;determining, based on the channel estimate, indication informationindicating at least one beam selected from a plurality of beams for aplurality of frequency locations in the predetermined frequency range;and transmitting to the network device the indication information in afirst part of a channel state information (CSI) report.

In a third aspect, there is provided a method implemented in a networkdevice. The method comprises receiving from a terminal device a channelstate information (CSI) report determined from a channel estimate, afirst part of the CSI report at least comprising first indicationinformation indicating at least one of a set of beams, and a second partof the CSI report at least comprising second indication informationindicating a plurality of frequency locations in a predeterminedfrequency range for the at least one selected beam; and constructing CSIbased on the first and second indication information to controltransmission with the terminal device.

In a fourth aspect, there is provided a method implemented in a networkdevice. The method comprises receiving from a terminal device a channelstate information (CSI) report determined from a channel estimate, afirst part of the CSI report at least comprising indication informationindicating at least one beam selected from a plurality of beams for aplurality of frequency locations in a predetermined frequency range; andconstructing CSI based on the first and second indication information tocontrol transmission with the terminal device.

In a fifth aspect, there is provided a terminal device. The deviceincludes a processor; and a memory coupled to the processing unit andstoring instructions thereon, the instructions, when executed by theprocessing unit, causing the device to perform the method according toany of the first and second aspects.

In a sixth aspect, there is provided a network device. The deviceincludes a processor; and a memory coupled to the processing unit andstoring instructions thereon, the instructions, when executed by theprocessing unit, causing the device to perform the method according toany of the third and fourth aspects.

In a seventh aspect, there is provided a computer readable medium havinginstructions stored thereon, the instructions, when executed on at leastone processor, causing the at least one processor to carry out themethod according to any of the first and second aspects.

In an eighth aspect, there is provided a computer readable medium havinginstructions stored thereon, the instructions, when executed on at leastone processor, causing the at least one processor to carry out themethod according to any of the first and second aspects.

Other features of the present disclosure will become easilycomprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some embodiments of the presentdisclosure in the accompanying drawings, the above and other objects,features and advantages of the present disclosure will become moreapparent, wherein:

FIG. 1 is a block diagram of a communication environment in whichembodiments of the present disclosure can be implemented;

FIG. 2 is a flowchart illustrating a process for channel stateinformation (CSI) transmission according to some embodiments of thepresent disclosure;

FIGS. 3A-3B illustrates graphs of time-domain and frequency-domainresponses of beams according to some other embodiments of the presentdisclosure;

FIGS. 4A-4B illustrates graphs of frequency-domain responses of beamsaccording to some other embodiments of the present disclosure;

FIGS. 5A-5B illustrates graphs of time-domain responses of beamsaccording to some other embodiments of the present disclosure;

FIGS. 6A-6B illustrates graphs of time-domain responses of beamsaccording to some other embodiments of the present disclosure;

FIG. 7 is a flowchart illustrating a process for CSI transmissionaccording to some further embodiments of the present disclosure;

FIG. 8 shows a flowchart of an example method in accordance with someembodiments of the present disclosure;

FIG. 9 shows a flowchart of an example method in accordance with someother embodiments of the present disclosure;

FIG. 10 shows a flowchart of an example method in accordance with somefurther embodiments of the present disclosure;

FIG. 11 shows a flowchart of an example method in accordance with someother yet further embodiments of the present disclosure; and

FIG. 12 is a simplified block diagram of a device that is suitable forimplementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numeralsrepresent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with referenceto some example embodiments. It is to be understood that theseembodiments are described only for the purpose of illustration and helpthose skilled in the art to understand and implement the presentdisclosure, without suggesting any limitations as to the scope of thedisclosure. The disclosure described herein can be implemented invarious manners other than the ones described below.

In the following description and claims, unless defined otherwise, alltechnical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skills in the art to which thisdisclosure belongs.

As used herein, the term “network device” or “base station” (BS) refersto a device which is capable of providing or hosting a cell or coveragewhere terminal devices can communicate. Examples of a network deviceinclude, but not limited to, a Node B (NodeB or NB), an Evolved NodeB(eNodeB or eNB), a NodeB in new radio access (gNB) a Remote Radio Unit(RRU), a radio head (RH), a remote radio head (RRH), a low power nodesuch as a femto node, a pico node, and the like. For the purpose ofdiscussion, in the following, some embodiments will be described withreference to eNB as examples of the network device.

As used herein, the term “terminal device” refers to any device havingwireless or wired communication capabilities. Examples of the terminaldevice include, but not limited to, user equipment (UE), personalcomputers, desktops, mobile phones, cellular phones, smart phones,personal digital assistants (PDAs), portable computers, image capturedevices such as digital cameras, gaming devices, music storage andplayback appliances, or Internet appliances enabling wireless or wiredInternet access and browsing and the like.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The term “includes” and its variants are to be read as openterms that mean “includes, but is not limited to.” The term “based on”is to be read as “based at least in part on.” The term “one embodiment”and “an embodiment” are to be read as “at least one embodiment.” Theterm “another embodiment” is to be read as “at least one otherembodiment.” The terms “first,” “second,” and the like may refer todifferent or same objects. Other definitions, explicit and implicit, maybe included below.

In some examples, values, procedures, or apparatus are referred to as“best,” “lowest,” “highest,” “minimum,” “maximum,” or the like. It willbe appreciated that such descriptions are intended to indicate that aselection among many used functional alternatives can be made, and suchselections need not be better, smaller, higher, or otherwise preferableto other selections.

FIG. 1 shows an example communication network 100 in whichimplementations of the present disclosure can be implemented. Thenetwork 100 includes a network device 110 and a terminal device 120served by the network device 110. The serving area of the network device110 is called as a cell 102. It is to be understood that the number ofnetwork devices and terminal devices is only for the purpose ofillustration without suggesting any limitations. The network 100 mayinclude any suitable number of network devices and terminal devicesadapted for implementing implementations of the present disclosure.Although not shown, it is to be understood that one or more terminaldevices may be located in the cell 102 and served by the network device110.

In the communication network 100, the network device 110 can communicatedata and control information to the terminal device 120 and the terminaldevice 120 can also communication data and control information to thenetwork device 110. A link from the network device 110 to the terminaldevice 120 is referred to as a downlink (DL) or a forward link, while alink from the terminal device 120 to the network device 110 is referredto as an uplink (UL) or a reverse link.

Depending on the communication technologies, the network 100 may be aCode Division Multiple Access (CDMA) network, a Time Division MultipleAddress (TDMA) network, a Frequency Division Multiple Access (FDMA)network, an Orthogonal Frequency-Division Multiple Access (OFDMA)network, a Single Carrier-Frequency Division Multiple Access (SC-FDMA)network or any others. Communications discussed in the network 100 mayuse conform to any suitable standards including, but not limited to, NewRadio Access (NR), Long Term Evolution (LTE), LTE-Evolution,LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA),Code Division Multiple Access (CDMA), cdma2000, and Global System forMobile Communications (GSM) and the like. Furthermore, thecommunications may be performed according to any generationcommunication protocols either currently known or to be developed in thefuture. Examples of the communication protocols include, but not limitedto, the first generation (1G), the second generation (2G), 2.5G, 2.75G,the third generation (3G), the fourth generation (4G), 4.5G, the fifthgeneration (5G) communication protocols. The techniques described hereinmay be used for the wireless networks and radio technologies mentionedabove as well as other wireless networks and radio technologies. Forclarity, certain aspects of the techniques are described below for LTE,and LTE terminology is used in much of the description below.

In communications, the terminal device 120 is configured to estimate andreport channel state information (CSI) of a communication channelbetween the terminal device 120 and the network device 110. The CSI canbe determined by the terminal device 120 using downlink referencesignals transmitted by the network device 110.

Generally, LTE utilizes an implicit rank indicator/precoding matrixindicator/resource partitioning information/channel quality indicator(RI/PMI/RPI/CQI) feedback framework for the CSI feedback. The CSIfeedback framework is “implicit” in the form of CQI/PMI/RI (and CRI inthe LTE specification) derived from a codebook.

RI is information on a channel rank as described above and indicates thenumber of streams that can be received via the same time-frequencyresource. Since RI is determined by long-term fading of a channel, itmay be generally fed back at a cycle longer than that of PMI or CQI. PMIis a value indicating a spatial characteristic of a channel andindicates a precoding matrix index of the network device preferred bythe terminal device. RPI is corresponding to power domain resourceassignments between the serving network device 110 and one or morenon-serving network devices. CQI is information indicating the strengthof a channel and indicates a reception SINR obtainable when the networkdevice uses PMI.

The CSI feedback reflects average channel conditions over the overall orpart of system bandwidth. Some metrics, such as RI, PMI, and RPI, may becomputed to reflect the average channel conditions across the systembandwidth (e.g., wideband RI/PMI). The PMI across the system bandwidthmay indicate an index of a beam for the system bandwidth, and the RPIacross the system bandwidth may indicate a gain of the beam across thesystem bandwidth. Some metrics, such as PMI and CQI, may be computed persubband. The PMI for a subband may indicate a gain of the beam in thesubband, and the RPI for a subband may indicate a phase shift of thebeam in the subband.

When the terminal device reports CSI for one beam, parameters definingthe RI, PMI, RPI, and/or CQI may be determined by the terminal devicebased on the channel estimate. The parameters may be reported to thenetwork device to identify a codeword from a codebook. The codebookdefined for transmission using one beam may also be referred to as atype I codebook, where each codeword therein can be defined as below:

$\begin{matrix}{W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P_{{CSI} - {RS}}}}\begin{bmatrix}v_{l,m} \\{\varphi_{n}v_{l,m}}\end{bmatrix}}} & \left. 1 \right)\end{matrix}$

where v_(l,m) indicates a vector for the specific beam; l and m areindices used to identify the beam, which are respectively correspondingto the horizontal and vertical directions of the beam because this beamis a three-dimensional (3D) beam; φ_(n) is used to define a polarizationfactor for the beam, and where

φ_(n) = e^(jπn/2) $u_{m} = \left\{ \begin{matrix}\begin{bmatrix}1 & \begin{matrix}e^{j\frac{2\pi m}{O_{2}N_{2}}} & \begin{matrix}\ldots & e^{j\frac{2\pi{m({N_{2} - 1})}}{O_{2}N_{2}}}\end{matrix}\end{matrix}\end{bmatrix} & {N_{2} > 1} \\1 & {N_{2} = 1}\end{matrix} \right.$ ${v_{l,m} = \begin{bmatrix}\begin{matrix}\begin{matrix}u_{m} & {e^{j\frac{2\pi l}{O_{1}N_{1}}}u_{m}}\end{matrix} & \ldots\end{matrix} & {e^{j\frac{2\pi{l({N_{1} - 1})}}{O_{1}N_{1}}}u_{m}}\end{bmatrix}^{T}},$

and

N₁, N₂, are used to indicate a dimension of an antenna array at thenetwork device, O₁, and O₂ are configured numbers for oversampling thespatial directions.

To allow the network device to determine the codeword for the beam,parameters including l, m, and φ_(n) are needed to be reported by theterminal device. Since CSI for only one beam is required, the overheadis limited.

In some other cases, the terminal device is configured to report CSI formore than one beam (for example, L beams). Information for the beams isrequired to determine the codeword from a codebook. The codeword in thiscase can be defined by the terminal device depending on information ofdifferent beams, for example as below:

$\begin{matrix}{W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},c_{l}}^{l} = {\frac{1}{\sqrt{N_{1}N_{2}{\sum\limits_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}}\left\lbrack \begin{matrix}{\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\{\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i +}}}}\end{matrix} \right.}} & \left. 2 \right)\end{matrix}$

where v_(m) ₁ _((i)) _(,m) ₂ _((i)) represents a vector for a i-th beam;m₁ ^((i)) and m₂ ^((i)) are indices corresponding to the horizontal andvertical direction of the i-th beam and can be used to identify the i-thbeam; v_(m) ₁ _((i)) _(,m) ₂ _((i)) may be regarded as a PMI for thei-th beam across a system bandwidth (a wideband) in some examples;p_(l,i) ⁽¹⁾ indicates a gain of the i-th beam across the systembandwidth, and p_(l,i) ⁽²⁾ indicates a gain of the i-th beam in acertain subband; p_(l,i) ⁽¹⁾ and p_(l,i) ⁽²⁾ may be regarded as a RPIfor the i-th beam across the system bandwidth and another PMI for thei-th beam in the certain subband; φ_(l,i) represents a phase factor inthe frequency domain for combining different beams. The codebookincluding a codeword such as in Equation (2) may be referred to as atype II codebook.

To allow the network device to determine the codeword, for each of the Lbeams, parameters including wideband information m₁ ^((i)), m₂ ^((i)),and p_(l,i) ⁽¹⁾, and suband information p_(l,i) ⁽²⁾, and φ_(l,i) areneeded to be reported by the terminal device, which will increase theoverhead for CSI transmissions. The total overhead for transmitting CSIis depending on the rank order and the number of beams to be reported.The following Table 1 shows the overhead for the CSI transmission insome cases.

TABLE 1 Type II CSI feedback overhead (in bits) for a single panel[0002] [0005] [0007] [0009] [0011] [0013 [0015 [0017] I MI1 PI otal MI2PI QI Total [0001] [0003] [0006] [0008] [0010] [0012] [0014 [0016][0018] Parameters WB) [0004] WB) WB) WB) SB) SB) SB) (WB + SB) [0019][0025] [002 [0027] [0028] [0029] [0030] [0031] [0032 

[0033] [0034] 1 (N₁, N₂) = I = 1 =2 3 3 83 [0020] [0035] [0036] [0037][0038] [0039] [0040 

[0041] 2 (4, 4) =3 7 5 3 3 33 [0021] [0042] [0043] [0044] [0045] [0046][0047 

[0048] 3 [0022] =4 8 1 0 9 20 (O₁, O₂) = [004 [0050] [0051] [0052][0053] [0054] [0055 

[0056] 3 [0023] I = 2 =2 5 8 4 8 14 (4, 4) [0057] [0058] [0059] [0060][0061] [0062

[0063] 4 [0024] =3 0 0 1 6 11 [0064] [0065] [0066] [0067] [0068] [0069 

[0070] 5 =4 1 2 4 8 0 84

indicates data missing or illegible when filed

As can be seen from Table 1, the overhead for the CSI feedback is largeand sometimes is about 600 bits. In addition if the system bandwidth iswide, the CSI feedback for each of a plurality of subbands in the systembandwidth is to be transmitted, which will further increase the overheadas the number of the subbands increase. Therefore, there is a need tocompress the overhead for the CSI transmission.

There have been some solutions for CSI compression. According to onesolution, a terminal device transmits CSI at some of frequency locationsin the frequency domain. Upon reception of the CSI feedback, the networkdevice determines the CSI at other frequency locations by interpolatingthe CSI received at some of the frequency locations. In this way, CSI atall the frequency locations can be determined while the overall overheadfor CSI transmission can be reduced. However, the CSI overhead is stilllarge and will also increase as the system bandwidth increases or thenumber of subbands increases.

According to embodiments of the present disclosure, there is prosed asolution for CSI transmission. In this solution, indication informationrelated to a frequency domain is determined and included in a CSI reportby a terminal device. The frequency-related indication information alongwith other indication information related to a beam in a spatial domaincan be used to construct CSI by a network device.

Principle and implementations of the present disclosure will bedescribed in detail below with reference to FIG. 2 , which shows aprocess 200 for UCI transmission according to an implementation of thepresent disclosure. For the purpose of discussion, the process 200 willbe described with reference to FIG. 1 . The process 200 may involve thenetwork device 110 and the terminal device 120 in FIG. 1 .

The terminal device 120 performs (205), a channel estimate between theterminal device 120 and the network device 110 across a predeterminedfrequency range for a set of beams having different spatial directions.Various procedures can be utilized for the terminal device 120 toperform the channel estimate. Typically, the terminal device 120 mayreceive a reference signal from the network device 110. The referencesignal may be any signal sequence that is known by both the terminaldevice 120 and the network device 110. By comparing the receivedreference signal and the true reference signal, the terminal device 120may estimate channel conditions between the terminal device 120 and thenetwork device 110.

The terminal device 120 determines (210), based on the channel estimate,first indication information indicating at least one beam selected fromthe set of beams and second indication information indicatingfrequency-related information for the at least one selected beam at aplurality of frequency locations in the predetermined frequency range.Depending on the channel estimate, the terminal device 120 selects apredetermined number of beams from a set of beams to report to thenetwork device. Each of the selected beam(s) can be indicated withcorresponding indices, for example, indices related to the horizontaland vertical directions.

According to embodiments of the present disclosure, additionalindication information (i.e., the second indication information) in thefrequency domain is determined for CSI feedback. The frequency range hasa system bandwidth of the network 100, and thus may be referred to as awideband. For each selected beam, the corresponding frequency-relatedinformation is indicated in the second indication information. In someembodiments, with the frequency-related information, a codeword for CSIcan be extended from Equation (2) as below:

$\begin{matrix}{{{\overset{\sim}{W}}_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},c_{l}}^{l} = {{H\left( {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},c_{l}}^{l},f_{i}} \right)} = {\frac{1}{\sqrt{N_{1}N_{2}{\Sigma}_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}\begin{bmatrix}{\sum\limits_{i = 0}^{L - 1}{{v_{m_{1}^{(i)},m_{2}^{(i)}} \otimes f_{i}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\{\sum\limits_{i = 0}^{L - 1}{{v_{m_{1}^{(i)},m_{m_{2}}^{(i)}} \otimes f_{i}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,{i + L}}}}\end{bmatrix}}}},{l = {1,2}}} & (3)\end{matrix}$

where f_(i) represents the frequency-related information for the i-thselected beam, L represents the number of selected beams, φ_(l,i)represents a co-phase shift factor in time domain for combiningdifferent beams, p_(l,i) ⁽¹⁾ and p_(l,i) ⁽²⁾ represents the gain of thei-th beam in time domain.

In some embodiments, the second indication information may be indicatedusing the result of time-to-frequency domain transformation performed atthe terminal device 120. For example, the second indication informationmay be indicated using an element selected from a resulting matrix of aFast Fourier Transformation (FFT) or a Discrete Fourier Transformation(DFT), which is usually performed at the terminal device 120, especiallyin an OFDM network. In the DFT matrix, each of the rows is correspondingto a subcarrier, and each of the columns is corresponding to a delayvalue in a time domain of a channel path that is associated with acertain selected beam. Therefore, elements in a certain row and acertain column in the DFT matrix can be used as the frequency-relatedinformation for CSI feedback.

An example DFT matrix is provided as below:

$\begin{matrix}{{f_{i}\overset{\bigtriangleup}{\rightarrow}{DFT}} = \begin{bmatrix} & \ldots & \\ & D_{s_{k},i} & \\ \vdots & D_{s_{k + 1},i} & \vdots \\ & D_{s_{k + 2},i} & \\ & \ldots & \end{bmatrix}} & (4)\end{matrix}$${{{where}D_{s_{k},i}} = e^{j2\pi s_{k}\tau_{i}}},{s_{k} = {- \frac{f\left( {{SB}_{k},{offset}} \right)}{N}}},$

and τ_(i)=0, . . . , N−1. In Equation (4), N is related to the size ofthe DFT matrix (i.e., a size of N*N); τ_(i) represents a delay valueassociated with the i-th beam in a time domain and may be normalized toa value in a range from 0 to N−1; s_(k) and i are the row and columnindices for an element in the DFT matrix, respectively; SB_(k)represents the k-th subband; SB_(k) and offset are used to determine therow index which is corresponding to a certain subcarrier in a subband;and offset may be an index of a center subcarrier in the subband (thesubband may be divided into one or more subcarriers) or an index of anon-center subcarrier but is a preconfigured parameter offset fordefining a certain subcarrier in a subband.

In some embodiments, the frequency-related information f_(i) for thei-th beam may be a vector including elements corresponding to aplurality of frequency locations (such as the frequency locations ofdifferent subbands in a certain frequency range). The length of thevector for the frequency-related information f_(i) depends on the numberof the frequency locations (for example, subbands), which may beconfigured by the network device 110. For example, the network device110 may notify the terminal device 120 that frequency-relatedinformation for S subbands is required to be reported and thus thefrequency-related information f_(i) has a length of S. The k-th elementin the vector for frequency-related information f_(i) may be representedas D_(s) _(k) _(,i).

In some embodiments, since the DFT matrix can be obtained at the networkdevice 110 and the subbands that are considered are also configured bythe network device 110, the terminal device 120 may determine only thedelay value associated with the selected beam (r_(i) for the pathassociated with the i-th beam) as the second indication information. Inthese embodiments, the frequency-related information for each selectedbeam can be indicated by a combination of the associated delay value andpredefined indices of the plurality of frequency locations (for example,s_(k)).

FIGS. 3A-3B illustrates graphs 302 and 304 for a time-domain responseand a frequency-domain response, respectively. The graph 302 for thetime-domain responses of all the beams may be determined as h(t)=Σ_(i=0)^(L-1)p_(l,i) ⁽¹⁾p_(l,i) ⁽²⁾φ_(l,i)δ(t−τ_(i)), where p_(l,i) ⁽¹⁾ p_(l,i)⁽²⁾ represents a gain of the i-th beam, and φ_(l,i) represents aco-phase shift factor for the i-th beam in the time domain appliedacross a plurality of frequency locations. The graph 304 for thefrequency-domain response for the i-th beam may be determined as H(i,l)=Σ_(i=0) ^(N-1)p_(l,i) ⁽¹⁾p_(l,i) ⁽²⁾φ_(l,i)e^(−j2πs) ^(k) ^(τ) ^(i) .

In some embodiments, instead of using the range from 0 to N−1, a valuerange of the delay value τ_(i) may also be configured, for example, viaradio resource control (RRC) signaling or activated by a media accesscontrol (MAC)-control element (CE). In some other embodiments, the rangeof the delay value τ_(i) is determined by a length of a cyclic prefixand/or the numerology used in the network 100.

In some embodiments, except the second indication information, otherinformation in the CSI report is reused from the conventional CSIfeedback framework. For example, the first indication informationindicating the selected beam(s) may be represented by the indices of thehorizontal and vertical directions of the selected beam(s) to indicatev_(m) ₁ _((i)) _(,m) ₂ _((i)) , which may be regarded as, for example, awideband PMI. In some embodiments, the terminal device 120 maydetermine, based on the channel estimate, third indication informationindicating a gain for the at least one selected beam across thefrequency range. For example, the third indication information may be awideband RPI indicating a gain of a beam (such as p_(l,i) ⁽¹⁾).

The terminal device 120 may further determine, based on the channelestimate, fourth indication information indicating a respectiveco-phasing shift in the time domain for the at least one selected beamapplied across the predetermined frequency range (such as φ_(l,i)). Thefourth indication information may be regarded as wideband information.

Referring back to FIG. 2 , the terminal device 120 transmits (215) thefirst indication information in a first part of a CSI report and thesecond indication information in a second part of the CSI report. A CSIreport typically includes two parts, the first part (also referred to aspart 1) and the second part (also referred to as part 2). The first partmay be transmitted by the terminal device 120 to the network device 110before the second part. The two parts may be encoded independently. Theindication information indicating the selected beam(s) by the terminaldevice 120 is generally in the first part such that the network device110 can first decode the first part to determine which beam(s) are to beexpected.

In embodiments where the third and fourth indication information isdetermined, the terminal device 120 may also include the determinedinformation in the second part of the CSI report to be transmitted tothe network device 110. Upon reception of the first and second parts ofthe CSI report, the network device 110 constructs (220) CSI based on thereceived indication information. For example, the network device 110determines a codeword from a CSI codebook based on the receivedindication information to control transmission with the terminal device120.

In some embodiments, a gain of a beam in each subband is not determinedor included in the CSI report. The CSI report may mainly include thefirst indication information indicating the selected beam(s) (forexample, v_(m) ₁ _((i)) _(,m) ₂ _((i)) ), the second indicationinformation (the delay value τ_(i)) for each selected beam, the thirdindication information across the frequency range (p_(l,i) ⁽¹⁾), and thefourth indication information indicating a co-phasing shift in the timedomain applied across the whole frequency range (φ_(l,i)). That is tosay, the gains of each selected beam and co-phasing shifts are reportedin the time domain, and thus not reported independently for each subbandat respective frequency locations in the CSI report, which may helpreduce the overhead for the report transmission. In some embodiments,the CSI report may further comprise further indication informationindicating a channel quality indicator (CQI) corresponding to thefrequency range. The CQI may be included in the first part of thereport.

In these embodiments, upon reception of the indication information, toconstruct the CSI, the network device 110 may determine, based on thereceived indication information, a codeword from a codebook configuredfor the CSI. The codeword may be determined, for example, according tothe above Equation (3). The codeword may be determined for each of thesubcarriers (the frequency locations). If there is only one beam in thecommunication channel, the beam indicated by v_(m) ₁ _((i)) _(,m) ₂_((i)) is the same for all the frequency locations, the gain of the beamacross the frequency range is the same for all the frequency locations,and the co-phasing shifts in the time domain is also the same for allthe frequency locations across the system bandwidth. The component phaseinformation in a subcarrier s_(k) is determined as φ_(l,i) e^(−j2πs)^(k) ^(τ) ^(i) , which is determined by the co-phasing shift in the timedomain and the delay value. In this case, the frequency-domain responseof a single beam in all the frequency range remains unchanged, as shownin graph 402 in FIGS. 4A-4B.

In some embodiments, if there are more than two beams selected, gainsfor each selected beam at the frequency locations may be determined byweighting the second, third, and fourth indication information of therespective selected beams. For example, if there are two selected beams,the second indication information may include delay values τ_(i) and τ₂for the two beams, the third indication information may include gains p₁and p₂ for the two beams applied across the frequency range, and thefourth indication information may include co-phasing shifts φ_(i) and φ₂in the time domain for the two beams applied at different frequencylocations. The gains of the two beams at the respective frequencylocations f may then be determined as p₁ v₁ φ₁ e^(jπfτ) ¹ +p₂ v₂ φ₂e^(j2πfτ) ² , as denoted as curve 410 in graph 404 of FIGS. 4A-4B. Othermethod may also be utilized to determine the gains at different subbandsbased on the gains across the frequency range.

In some embodiments, to enable subband-based CSI reporting, part of thesubband information, instead of all the subband information isdetermined and transmitted in the report. For example, if there are twoor more beams selected (for example, L beams), the terminal device 120may further determine fifth indication information indicating gains ofat least one beam in the subset of beams at a subset of the plurality offrequency locations. For example, one or more strongest beams (forexample, Lsb) are selected from L beams and their subband-based gainscan be determined as the fifth indication information. In someembodiments, the plurality of frequency locations in the frequency rangemay be divided into two or more subsets. The strongest beams aresearched in each of the subsets. The fifth indication information may beregarded as the subband PMI, represented as p_(l,i) ⁽²⁾. By transmittingless subband gains, the overhead of the CSI may also be decreased. Thefifth indication information may be reported in the second part of theCSI report.

As an example, in FIGS. 5A-5B, graph 502 shows eight beams distributedin a time domain with different delay values, and graph 504 shows thefrequency-domain response. According to the strength of thefrequency-domain response, beams 1, 2, 4, and 8 are selected in thefirst set (set1) of frequency locations and their corresponding gains atthese frequency locations may be determined and included in the fifthindication. In addition, in the second set (set2) of frequencylocations, beams 1, 2, 7, and 8 are selected and their correspondinggains at these frequency locations may be determined and included in thefifth indication.

In some embodiments, instead of including the fourth indicationinformation for all the beams and at all the frequency locations, theCSI report may include sixth indication information indicatingrespective co-phasing shifts of the at least one stronger beam at thesubset of frequency locations. In the example of FIGS. 5A-5B, the fourthindication information may indicate co-phasing shifts of beams 1, 2, 4,and 8 at the first set of frequency locations in, and indicateco-phasing shifts of beams 1, 2, 7, and 8 at the second set offrequency. By transmitting less subband co-phasing shifts, the overheadof the CSI may be further decreased. The sixth indication informationmay also be reported in the second part of the CSI report.

In some embodiments, the CSI report may further comprise furtherindication information indicating a channel quality indicator (CQI)corresponding to the frequency range or respective CQIs corresponding tothe plurality of frequency locations. The CQI-related information may beincluded in the first part of the CSI report.

In some embodiments, to transmit the delay value τ_(i) in the CSItransmission by the terminal device 120, the delay value in the secondindication information may be quantized into a number of bits. To ensurethe accuracy as well as avoid using too much bits to increase theoverhead, some embodiments of the quantization for the delay value arediscussed below. Other information in the CSI report may be quantizedusing any currently existing methods or any other methods that will bedeveloped.

In some embodiments, the terminal device 120 may use a non-uniformquantization for the delay value τ_(i). In one embodiment, for eachdelay value for a selected beam the terminal device 120 may determine,based on the delay value τ_(i), a first number of bits for quantizationof the delay value, the first number being larger than the number ofbits determined for a further delay value with a smaller magnitude. Forexample, if a delay value is to be ranged from 0 to X, the lower themagnitude of the delay value τ_(i) is, the higher the first number is,and the higher the magnitude of the delay value τ_(i), the smaller thefirst number is. In this way, the small delay value τ_(i) may bequantized with more bits to improve the transmission accuracy andresolution relative to other small delay value. The following Table 2provides an example how the delay values with different values arequantized. In this example, a delay value can have a value ranged from 0to 144. It would be appreciated that Table 2 is provided for purpose ofillustration only and other quantization methods are also appreciated.

TABLE 2 Quantization of delay values based on their magnitudes Delayvalue step-size # of states  0-15 2 8 16-47 4 8 47-95 6 8  96-143 8 8

In a further embodiment, for each delay value for a selected beam theterminal device 120 may determine, based on a gain of the at least oneselected beam, a second number of bits for quantization of the delayvalue, the second number being larger than the number of bits determinedfor a further delay value corresponding to a further beam with a highergain. All the selected beams may be ranked according to their gains. Insome examples, the first beam in the time domain has the highest gain,and thus a number of delay values (for example, K) for the first K beamsmay be allocated with a large number of bits, while the remaining delayvalues may be allocated with a smaller number of bits. The followingTable 3 provides another example how different delay value arequantized. It would be appreciated that Table 3 is provided for purposeof illustration only and other quantization methods are alsoappreciated.

TABLE 3 Quantization of delay values based on their magnitudes Order ofgains Bits for delay value 1^(st)-Kth gains 5 Remaining gains 3

In some embodiments, the first beam may not be the strongest beam (nothave the highest gain) due to the synchronization procedure. Forexample, graph 602 of FIGS. 6A-6B shows the time-domain responses ofdifferent delay values in the time domain, where the first beamcorresponding to the response 610 is the synchronized first beam, whilethe seventh beam corresponding to the response 612 is the actual firstbeam with the smallest actual delay values. In these embodiments, foreach delay value, the terminal device 120 may modify the delay value byshifting the delay value with a cyclic-shift value to obtain acyclic-shifted version of the delay value. The cyclic-shift value may beconfigured by the network device 110. As show in graph 604 of FIGS.6A-6B, after cyclic shifting, the seventh beam, which is the actualfirst beam with the smallest gain, is shifted to be the first one andall the beams are gathered together to a specific time range. Theterminal device 120 may then determine the second number of bits basedon the gain of the cyclic-shifted version of the delay value.

Upon determining the number of the bits for quantization, the terminaldevice 120 may quantize the delay value into the first number of bits(in the embodiments of magnitude-based quantization) or into the secondnumber of bits (in the embodiments of gain-based quantization). In someembodiments, if the second number of bits is determined based on thecyclic-shifted version of the delay value, the terminal device 120 mayquantize the cyclic-shifted version of the delay value into the secondnumber of bits.

In the above embodiments, the frequency-related information is includedin the CSI report as separate information (i.e., τ_(i)). In some otherembodiments, the frequency-related information may be communicated in amore implicit manner with the indication information for the selectedbeam(s). Such embodiments will be described below with reference to FIG.7 , which shows a process 700 for UCI transmission according to animplementation of the present disclosure. For the purpose of discussion,the process 700 will be described with reference to FIG. 1 . The process700 may involve the network device 110 and the terminal device 120 inFIG. 1 .

The terminal device 120 performs (705), a channel estimate between theterminal device 120 and the network device 110 across a predeterminedfrequency range for a set of beams having different spatial directions.The operation at 705 is similar as the operation at 205, and thus thedetailed description is omitted here for brevity.

The terminal device 120 determines (710), based on the channel estimate,indication information indicating at least one beam selected from aplurality of beams for a plurality of frequency locations in thepredetermined frequency range. According to the embodiments, theindication information is specific to the beam both in thespatial-related information and the frequency-related information. Inother words, the indication information is applied for all frequencylocations. In these embodiments, the codebook for the CSI may beredesigned to represent such information. For example, a codeword forCSI can be extended from Equation (2) as below:

$\begin{matrix}{{{\overset{\sim}{W}}_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},c_{l}}^{l} = {\frac{1}{\sqrt{N_{1}N_{2}{\Sigma}_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}\begin{bmatrix}{\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)},f_{i}}^{\square}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\{\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)},f_{i}}^{\square}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,{i + L}}}}\end{bmatrix}}},{l = {1,2}}} & \left. 5 \right)\end{matrix}$

where v_(m) ₁ _((i)) _(,m) ₂ _((i)m,f) _(i) ^(□)=v_(m) ₁ _((i)) _(,m) ₂_((i)) ^(□⊗f) _(i′). Upon the channel estimate, the terminal device 120may determine information for indicating v_(m) ₁ _((i)) _(,m) ₂_((i)m,f) _(l) ^(□), which may include determine the indices for thei-th beam, m₁ ^((i)) and m₂ ^((i)), and the index for thefrequency-related information f_(i). The three indices may be determinedas the indication information. The index f may be determined in asimilar manner as described in the above embodiments of FIG. 2 . Theindex m₁ ^((i)) and m₂ ^((i)), and the index f_(i). can be encodedjointly or separately in the report.

The terminal device 120 transmits (715) the indication information tothe network device 110 in a first part of a CSI report. Different fromthe embodiments described with respect to FIG. 2 , the indicationinformation indicating the frequency-related information is reported tothe network device 110 together with the indication informationindicating the selected beam(s).

In addition to the above determined indication information, the CSIreport may also include a second part, which may include otherinformation, such as indication information indicating a respective gainin the time domain for the at least one selected beam applied across thepredetermined frequency range, indication information indicating arespective co-phasing shift in the time domain for the at least oneselected beam applied across the predetermined frequency range,indication information indicating a gain of at least one beam in thesubset of beams at at least one of the plurality of frequency locations,and/or indication information indicating a respective co-phasing shiftin the time domain for the at least one beam in the subset of beams atthe at least one frequency location. Such indication information may besimilar as those described in the above embodiments of FIG. 2 . In someembodiments, the first part of the CSI report may further includechannel quality indicator (CQI) corresponding to the wideband orrespective CQIs corresponding to the plurality of frequency locations.The first part may be first transmitted to the network device 110,followed by the second part.

Upon reception of the CSI report, the network device 110 constructs(720) CSI based on the received indication information. For example, thenetwork device 110 determines a codeword from a CSI codebook based onthe received indication information to control transmission with theterminal device 120.

FIG. 8 shows a flowchart of an example method 800 in accordance withsome embodiments of the present disclosure. The method 800 can beimplemented at a terminal device 120 as shown in FIG. 1 . For thepurpose of discussion, the method 900 will be described from theperspective of the terminal device 120 with reference to FIG. 1 .

At block 810, the terminal device 120 performs a channel estimatebetween the terminal device and a network device across a predeterminedfrequency range for a set of beams having different spatial directions.At block 820, the terminal device 120 determines, based on the channelestimate, first indication information indicating at least one beamselected from the set of beams and second indication informationindicating frequency-related information for the at least one selectedbeam at a plurality of frequency locations in the predeterminedfrequency range. At block 830, the terminal device 120 transmits to thenetwork device the first indication information in a first part of achannel state information (CSI) report and the second indicationinformation in a second part of the CSI report.

In some embodiments, determining the second indication informationcomprises: determining at least one delay value associated with the atleast one selected beam in a time domain applied across thepredetermined frequency range as the second indication information, thefrequency-related information for each selected beam being indicated bya combination of the associated delay value and predefined indices ofthe plurality of frequency locations.

In some embodiments, the plurality of frequency locations are configuredby the network device.

In some embodiments, the method further comprises determining, based onthe channel estimate, third indication information indicating arespective gain in a time domain for the at least one selected beamapplied across the predetermined frequency range and fourth indicationinformation indicating a respective co-phasing shift in the time domainfor the at least one selected beam applied across the predeterminedfrequency range; and transmitting to the network device the third andfourth indication information in the second part of the CSI report.

In some embodiments, the first indication information indicating asubset of beams selected from the set of beams, the subset of beamscomprising two or more beams, and the method further comprising:determining, based on the channel estimate, fifth indication informationindicating gains of at least one beam in the subset of beams at a subsetof the plurality of frequency locations, the at least one beam beingstronger than other beams in the subset of beams; and transmitting tothe network device the fifth indication information in the second partof the CSI report.

In some embodiments, the method further comprises determining, based onthe channel estimate, sixth indication information indicating respectiveco-phasing shifts of the at least one beam in the subset of beams at theat least one frequency location; and transmitting to the network devicethe sixth indication information in the second part of the CSI report.

In some embodiments, the first part of the CSI report further comprisesfurther indication information indicating a channel quality indicator(CQI) corresponding to the frequency range or respective CQIscorresponding to the plurality of frequency locations.

In some embodiments, the transmitting comprises: for each of the atleast one delay value, determining, based on a magnitude of the delayvalue, a first number of bits for quantization of the delay value, thefirst number being larger than the number of bits determined for afurther delay value with a smaller magnitude; quantizing the delay valueinto the first number of bits; and transmitting the first number of bitsto the network device.

In some embodiments, the transmitting comprises: for each of the atleast one beam, determining, based on a gain of the at least oneselected beam, a second number of bits for quantization of the delayvalue, the second number being larger than the number of bits determinedfor a further delay value corresponding to a further beam with a highergain; quantizing the delay value into the second number of bits; andtransmitting the second number of bits to the network device.

In some embodiments, determining the second number of bits comprises:modifying the delay value by shifting the delay value with acyclic-shift value to obtain a cyclic-shifted version of the delayvalue; and determining the second number of bits based on the gain ofthe cyclic-shifted version of the delay value. Quantizing the delayvalue comprises quantizing the cyclic-shifted version of the delayvalue.

In some embodiments, the predetermined frequency range has a systembandwidth.

In some embodiments, the second part is transmitted to the networkdevice after the first part is transmitted.

FIG. 9 shows a flowchart of an example method 900 in accordance withsome other embodiments of the present disclosure. The method 900 can beimplemented at a terminal device 120 as shown in FIG. 1 . For thepurpose of discussion, the method 900 will be described from theperspective of the terminal device 120 with reference to FIG. 1 .

At block 910, the terminal device 120 performs a channel estimatebetween the terminal device and a network device across a predeterminedfrequency range for a set of beams having different spatial directions.At block 920, the terminal device 120 determine, based on the channelestimate, indication information indicating at least one beam selectedfrom a plurality of beams for a plurality of frequency locations in thepredetermined frequency range. At block 930, the terminal device 120transmits to the network device the indication information in a firstpart of a channel state information (CSI) report.

In some embodiments, the indication information includes an index fordefining a codeword in a codebook configured for the CSI.

In some embodiments, the method further comprises determining, based onthe channel estimate, further indication information indicating at leastone of: a respective gain in a time domain for the at least one selectedbeam across the predetermined frequency range, a respective co-phasingshift in the time domain for the at least one selected beam appliedacross the predetermined frequency range; and transmitting to thenetwork device the indication information in a second part of the CSIreport, the second part being transmitted to the network device afterthe first part is transmitted.

FIG. 10 shows a flowchart of an example method 1000 in accordance withsome further embodiments of the present disclosure. The method 1000 canbe implemented at a network device 110 as shown in FIG. 1 . For thepurpose of discussion, the method 1000 will be described from theperspective of the terminal device 120 with reference to FIG. 1 .

At block 1010, the network device 110 receives from a terminal device achannel state information (CSI) report determined from a channelestimate, a first part of the CSI report at least comprising firstindication information indicating at least one of a set of beams, and asecond part of the CSI report at least comprising second indicationinformation indicating a plurality of frequency locations in apredetermined frequency range for the at least one selected beam. Atblock 1020, the network device 110 constructs CSI based on the first andsecond indication information to control transmission with the terminaldevice.

In some embodiments, the second indication information includes at leastone delay value associated with the at least one selected beam in a timedomain applied across the predetermined frequency range as the secondindication information, constructing the CSI comprising: determining thefrequency-related information for each selected beam by a combination ofthe associated delay value and predefined indices of the plurality offrequency locations.

In some embodiments, the plurality of frequency locations are configuredby the network device.

In some embodiments, the second part of the CSI report comprises thirdindication information indicating a respective gain in a time domain forthe at least one selected beam applied across the predeterminedfrequency range and fourth indication information indicating arespective co-phasing shift in the time domain for the at least oneselected beam applied across the predetermined frequency range, themethod further comprising: determining respective gains for the at leastone selected beam at the plurality of frequency locations by weightingthe second, third, and fourth indication information.

In some embodiments, the first indication information indicating asubset of beams selected from the set of beams, the subset of beamscomprising two or more beams, and the second part of the CSI reportfurther comprises fifth indication information indicating gains of atleast one beam in the subset of beams at a subset of the plurality offrequency locations, the at least one beam being stronger than otherbeams in the subset of beams.

In some embodiments, the second part of the CSI report further comprisessixth indication information indicating respective co-phasing shifts ofthe at least one beam in the subset of beams at the at least onefrequency location.

In some embodiments, the first part of the CSI report further comprisesfurther indication information indicating a channel quality indicator(CQI) corresponding to the frequency range or respective CQIscorresponding to the plurality of frequency locations.

In some embodiments, constructing the CSI comprises: determining, basedon the first and second indication information, a codeword from acodebook configured for the CSI.

In some embodiments, the second part is received by the network deviceafter the first part is received.

FIG. 11 shows a flowchart of an example method 1100 in accordance withsome yet further embodiments of the present disclosure. The method 1100can be implemented at a network device 110 as shown in FIG. 1 . For thepurpose of discussion, the method 1000 will be described from theperspective of the terminal device 120 with reference to FIG. 1 .

At block 1110, the network device 110 receives from a terminal device achannel state information (CSI) report determined from a channelestimate, a first part of the CSI report at least comprising indicationinformation indicating at least one beam selected from a plurality ofbeams for a plurality of frequency locations in a predeterminedfrequency range. At block 1220, the network device 110 constructs CSIbased on the first and second indication information to controltransmission with the terminal device.

In some embodiments, the indication information includes an index fordefining a codeword in a codebook configured for the CSI.

In some embodiments, a second part of the CSI report comprise furtherindication information indicating at least one of: a respective gain ina time domain for the at least one selected beam across thepredetermined frequency range, a respective co-phasing shift in the timedomain for the at least one selected beam applied across thepredetermined frequency range. The second part is received by thenetwork device after the first part is received.

FIG. 12 is a simplified block diagram of a device 1200 that is suitablefor implementing embodiments of the present disclosure. The device 1200can be considered as a further example implementation of a networkdevice 110 or a terminal device 120 as shown in FIG. 1 . Accordingly,the device 1200 can be implemented at or as at least a part of thenetwork device 110 or the terminal device 120.

As shown, the device 1200 includes a processor 1210, a memory 1220coupled to the processor 1210, a suitable transmitter (TX) and receiver(RX) 1240 coupled to the processor 1210, and a communication interfacecoupled to the TX/RX 1240. The memory 1210 stores at least a part of aprogram 1230. The TX/RX 1240 is for bidirectional communications. TheTX/RX 1240 has at least one antenna to facilitate communication, thoughin practice an Access Node mentioned in this application may haveseveral ones. The communication interface may represent any interfacethat is necessary for communication with other network elements, such asX2 interface for bidirectional communications between eNBs, S1 interfacefor communication between a Mobility Management Entity (MME)/ServingGateway (S-GW) and the eNB, Un interface for communication between theeNB and a relay node (RN), or Uu interface for communication between theeNB and a terminal device.

The program 1230 is assumed to include program instructions that, whenexecuted by the associated processor 1210, enable the device 1200 tooperate in accordance with the embodiments of the present disclosure, asdiscussed herein with reference to FIGS. 2 to 4 and FIGS. 9 to 12 . Theembodiments herein may be implemented by computer software executable bythe processor 1210 of the device 1200, or by hardware, or by acombination of software and hardware. The processor 1210 may beconfigured to implement various embodiments of the present disclosure.Furthermore, a combination of the processor 1210 and memory 1210 mayform processing means 1250 adapted to implement various embodiments ofthe present disclosure.

The memory 1210 may be of any type suitable to the local technicalnetwork and may be implemented using any suitable data storagetechnology, such as a non-transitory computer readable storage medium,semiconductor-based memory devices, magnetic memory devices and systems,optical memory devices and systems, fixed memory and removable memory,as non-limiting examples. While only one memory 1210 is shown in thedevice 1200, there may be several physically distinct memory modules inthe device 1200. The processor 1210 may be of any type suitable to thelocal technical network, and may include one or more of general purposecomputers, special purpose computers, microprocessors, digital signalprocessors (DSPs) and processors based on multicore processorarchitecture, as non-limiting examples. The device 1200 may havemultiple processors, such as an application specific integrated circuitchip that is slaved in time to a clock which synchronizes the mainprocessor.

Generally, various embodiments of the present disclosure may beimplemented in hardware or special purpose circuits, software, logic orany combination thereof. Some aspects may be implemented in hardware,while other aspects may be implemented in firmware or software which maybe executed by a controller, microprocessor or other computing device.While various aspects of embodiments of the present disclosure areillustrated and described as block diagrams, flowcharts, or using someother pictorial representation, it will be appreciated that the blocks,apparatus, systems, techniques or methods described herein may beimplemented in, as non-limiting examples, hardware, software, firmware,special purpose circuits or logic, general purpose hardware orcontroller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer programproduct tangibly stored on a non-transitory computer readable storagemedium. The computer program product includes computer-executableinstructions, such as those included in program modules, being executedin a device on a target real or virtual processor, to carry out theprocess or method as described above with reference to any of FIGS. 2 to11 Generally, program modules include routines, programs, libraries,objects, classes, components, data structures, or the like that performparticular tasks or implement particular abstract data types. Thefunctionality of the program modules may be combined or split betweenprogram modules as desired in various embodiments. Machine-executableinstructions for program modules may be executed within a local ordistributed device. In a distributed device, program modules may belocated in both local and remote storage media.

Program code for carrying out methods of the present disclosure may bewritten in any combination of one or more programming languages. Theseprogram codes may be provided to a processor or controller of a generalpurpose computer, special purpose computer, or other programmable dataprocessing apparatus, such that the program codes, when executed by theprocessor or controller, cause the functions/operations specified in theflowcharts and/or block diagrams to be implemented. The program code mayexecute entirely on a machine, partly on the machine, as a stand-alonesoftware package, partly on the machine and partly on a remote machineor entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium,which may be any tangible medium that may contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device. The machine readable medium may be a machinereadable signal medium or a machine readable storage medium. A machinereadable medium may include but not limited to an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatus,or device, or any suitable combination of the foregoing. More specificexamples of the machine readable storage medium would include anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing.

Further, while operations are depicted in a particular order, thisshould not be understood as requiring that such operations be performedin the particular order shown or in sequential order, or that allillustrated operations be performed, to achieve desirable results. Incertain circumstances, multitasking and parallel processing may beadvantageous. Likewise, while several specific implementation detailsare contained in the above discussions, these should not be construed aslimitations on the scope of the present disclosure, but rather asdescriptions of features that may be specific to particular embodiments.Certain features that are described in the context of separateembodiments may also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment may also be implemented in multipleembodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specificto structural features and/or methodological acts, it is to beunderstood that the present disclosure defined in the appended claims isnot necessarily limited to the specific features or acts describedabove. Rather, the specific features and acts described above aredisclosed as example forms of implementing the claims.

What is claimed is:
 1. A method implemented in a terminal device,comprising: performing a channel estimate between the terminal deviceand a network device across a predetermined frequency range for a set ofbeams having different spatial directions; determining, based on thechannel estimate, first indication information indicating at least onebeam selected from the set of beams and second indication informationindicating frequency-related information for the at least one selectedbeam at a plurality of frequency locations in the predeterminedfrequency range; transmitting to the network device the first indicationinformation in a first part of a channel state information (CSI) reportand the second indication information in a second part of the CSIreport; determining, based on the channel estimate, third indicationinformation indicating a respective gain in a time domain for the atleast one selected beam applied across the predetermined frequency rangeand fourth indication information indicating a respective co-phasingshift in the time domain for the at least one selected beam appliedacross the predetermined frequency range; and transmitting to thenetwork device the third and fourth indication information in the secondpart of CSI report.
 2. The method of claim 1, wherein determining thesecond indication information comprises: determining at least one delayvalue associated with the at least one selected beam in a time domainapplied across the predetermined frequency range as the secondindication information, the frequency-related information for eachselected beam being indicated by a combination of the associated delayvalue and predefined indices of the plurality of frequency locations. 3.The method of claim 1, wherein the plurality of frequency locations areconfigured by the network device.
 4. The method of claim 1, wherein thefirst indication information indicating a subset of beams selected fromthe set of beams, the subset of beams comprising two or more beams, andthe method further comprising: determining, based on the channelestimate, fifth indication information indicating gains of at least onebeam in the subset of beams at a subset of the plurality of frequencylocations, the at least one beam being stronger than other beams in thesubset of beams; and transmitting to the network device the fifthindication information in the second part of the CSI report.
 5. Themethod of claim 4, further comprising: determining, based on the channelestimate, sixth indication information indicating respective co-phasingshifts of the at least one beam in the subset of beams at the at leastone frequency location; and transmitting to the network device the sixthindication information in the second part of report of CSI.
 6. Themethod of claim 1, wherein the first part of the CSI report furthercomprises further indication information indicating a channel qualityindicator (CQI) corresponding to the frequency range or respective CQIscorresponding to the plurality of frequency locations.
 7. The method ofclaim 2, wherein the transmitting comprises: for each of the at leastone delay value, determining, based on a magnitude of the delay value, afirst number of bits for quantization of the delay value, the firstnumber being larger than the number of bits determined for a furtherdelay value with a smaller magnitude; quantizing the delay value intothe first number of bits; and transmitting the first number of bits tothe network device.
 8. The method of claim 2, wherein the transmittingcomprises: for each of the at least one beam, determining, based on again of the at least one selected beam, a second number of bits forquantization of the delay value, the second number being larger than thenumber of bits determined for a further delay value corresponding to afurther beam with a higher gain; quantizing the delay value into thesecond number of bits; and transmitting the second number of bits to thenetwork device.
 9. The method of claim 8, wherein determining the secondnumber of bits comprises: modifying the delay value by shifting thedelay value with a cyclic-shift value to obtain a cyclic-shifted versionof the delay value; and determining the second number of bits based onthe gain of the cyclic-shifted version of the delay value, and whereinquantizing the delay value comprises quantizing the cyclic-shiftedversion of the delay value.
 10. The method of claim 1, wherein thepredetermined frequency range has a wideband.
 11. The method of claim 1,wherein the second part is transmitted to the network device after thefirst part is transmitted.
 12. A method implemented in a terminaldevice, comprising: performing a channel estimate between the terminaldevice and a network device across a predetermined frequency range for aset of beams having different spatial directions; determining, based onthe channel estimate, indication information indicating at least onebeam selected from a plurality of beams for a plurality of frequencylocations in the predetermined frequency range; transmitting to thenetwork device the indication information in a first part of a channelstate information (CSI) report; determining, based on the channelestimate, further indication information indicating at least one of: arespective gain in a time domain for the at least one selected beamapplied across the predetermined frequency range, a respectiveco-phasing shift in the time domain for the at least one selected beamapplied across the predetermined frequency range; and transmitting tothe network device the indication information in a second part of theCSI report, the second part being transmitted to the network deviceafter the first part is transmitted.
 13. The method of claim 12, whereinthe indication information includes an index for defining a codeword ina codebook configured for the CSI.
 14. A method implemented in a networkdevice, comprising: receiving from a terminal device a channel stateinformation (CSI) report determined from a channel estimate, a firstpart of the CSI report at least comprising first indication informationindicating at least one of a set of beams, and a second part of the CSIreport at least comprising second indication information indicating aplurality of frequency locations in a predetermined frequency range forthe at least one selected beam; and constructing CSI based on the firstand second indication information to control transmission with theterminal device, wherein the second part of the CSI report comprisesthird indication information indicating a respective gain in a timedomain for the at least one selected beam applied across thepredetermined frequency range and fourth indication informationindicating a respective co-phasing shift in the time domain for the atleast one selected beam applied across the predetermined frequencyrange, the method further comprising: determining respective gains forthe at least one selected beam at the plurality of frequency locationsby weighting the second, third, and fourth indication information. 15.The method of claim 14, wherein the second indication informationincludes at least one delay value associated with the at least oneselected beam in a time domain applied across the predeterminedfrequency range as the second indication information, constructing theCSI comprising: determining the frequency-related information for eachselected beam by a combination of the associated delay value andpredefined indices of the plurality of frequency locations.
 16. Themethod of claim 14, wherein the first indication information indicatinga subset of beams selected from the set of beams, the subset of beamscomprising two or more beams, and the second part of the CSI reportfurther comprises fifth indication information indicating gains of atleast one beam in the subset of beams at a subset of the plurality offrequency locations, the at least one beam being stronger than otherbeams in the subset of beams, and wherein the second part of the CSIreport further comprises sixth indication information indicatingrespective co-phasing shifts of the at least one beam in the subset ofbeams at the at least one frequency location, and wherein the first partof the CSI report further comprises further indication informationindicating a channel quality indicator (CQI) corresponding to thefrequency range or respective CQIs corresponding to the plurality offrequency locations.